Problem: $ E = \left[\begin{array}{rrr}0 & 2 & 1 \\ 2 & 0 & 0 \\ 2 & 2 & 2\end{array}\right]$ What is $ E^{-1}$ ?
Explanation: $ = \left[\begin{array}{rrr}0 & \frac{1}{2} & 0 \\ 1 & \frac{1}{2} & -\frac{1}{2} \\ -1 & -1 & 1\end{array}\right]$